Variation of Forehead Temperature during Routine Working Shift in Hospital Laboratory Personnel: Implications for SARS-CoV-2 Screening

BACKGROUND: Scarce information is available on circadian body temperature fluctuation in healthy healthcare workers. METHODS: Forehead temperature was measured with an infrared thermometer in 33 ostensibly healthy laboratory professionals (mean age, 43 ± 13 years; 76% females) throughout a regular working shift, from 800 AM to 300 PM, at 1-hour intervals. RESULTS: A significant difference was found at different times of the day by 1-way analysis of variance (F statistics, 13.79; p < 0.001). The lowest mean forehead temperature was 36.2 ± 0.3℃, recorded at 100 PM, whilst the highest was 36.7 ± 0.3℃, at 900 AM. The mean difference between forehead temperature at acrophase and nadir was 0.5℃ (95% CI, 0.3-0.6℃; p < 0.001). The forehead temperature measured between 900-1200 AM was also significantly higher than that measured between 100-300 PM (0.3℃; 95% CI, 0.2-0.4℃; p < 0.001). The mean intra-individual variation of forehead temperature was higher but not significantly different in men (1.0 ± 0.2%) compared to women (0.8 ± 0.3%; p = 0.112). CONCLUSION: Fever screening protocols for purposes of coronavirus disease 2019 (COVID-19) and other infectious diseases monitoring should consider normal daily fluctuations in forehead temperature.